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Several years ago, DMC (metsulfuron) and TFC (chlorsulfuron) were marketed for use in warm-season turfgrasses. DMC was sold by O. M. Scotts, and TFC was sold by Lesco. However, the active ingredients - metsulfuron and chlorsulfuron - were manufactured by DuPont. Sometime in 1995, DuPont made a decision to remove these herbicides from the turfgrass market. But there is good news, Riverdale Chemical Company has reintroduced these postemergence herbicides for use in warm-season turfgrasses. Metsulfuron will be sold under the trade name of Manor and chlorsulfuron will be sold under the trade name of Corsair.

Both metsulfuron and chlorsulfuron belong to the sulfonylurea herbicide family. Members of this family have extremely low toxicity to animals, but are highly phytotoxic to susceptible weeds at very low rates. For example, Manor, a 60 DF formulation, is labeled for use on Kentucky bluegrass, bermudagrass, centipedegrass, St. Augustinegrass and zoysiagrass at rates that range from 0.25 to 1.0 dry ounce of product per acre. At labeled rates warm-season turfgrasses and Kentucky bluegrass have excellent tolerance to metsulfuron. Chlorsulfuron is labeled for use in Kentucky bluegrass, bahiagrass and bermudagrass. While this herbicide can be applied on a broadcast basis, it primarily was used as a spot treatment to control clumpy tall fescue in labeled turfgrasses. Metsulfuron and chlorsulfuron inhibit the production of valine, leucine and isoleucine. These amino acids are used by plants to make proteins of which many serve as enzymes that catalyze the various biochemical reactions in plants. When amino acid synthesis is prevented, key enzymes are not produced and the weed slowly dies over a period of 1 to 3 weeks.

Manor provides excellent postemergence control of Pensacola bahiagrass, ryegrass, wild garlic and onion, and numerous broadleaf weeds (Table 1). Unlike phenoxy/dicamba herbicides (numerous trade names) and imazaquin (Image), metsulfuron does not temporarily delay the spring transition of bermudagrass. Additionally, in overseeding situations, Manor may be used at low rates on bermudagrass putting greens, and at slightly higher rates on bermudagrass fairways to hasten the transition from ryegrass to bermudagrass.

While Manor and Corsair control a wide range of weed species, these herbicides do not control summer annual grasses such as crabgrass, goosegrass and sandbur. Other weeds not controlled by these herbicides include dallisgrass, vaseygrass, broomsedge, carpetweed, johnsongrass and yellow thistle. Thus similar to all other selective turfgrass herbicides, the use of Manor and Corsair should be dictated by the weed species composition of a labeled turfgrass species.

Manor is excellent herbicide for use on warm-season turfgrasses, particularly St. Augustinegrass. This turfgrass species has very low tolerance to 2,4-D/dicamba containing herbicides which has greatly compounded the difficulty of controlling broadleaf weeds. However, St. Augustinegrass has excellent tolerance to Manor, and Manor controls numerous problem broadleaf weed species.

Both Manor and Corsair will be sold in the spring of 2000. Check with your turfgrass herbicide dealer or contact Riverdale Chemical Company at 1-800-345-3330 or at www.riverdalecc.com for additional information.

Table 1. Estimates of Weed Control with Metsulfuron (Manor)¹

¹Compiled by John Boyd, Univ. of Arkansas,;Jim Taylor, Mississippi State Univ.; Tim Murphy, Univ. of Georgia; Fred Yelverton, North Carolina State Univ.; and Bert McCarty, Clemson Univ.